A powder-liquid curable material kit used in the field of dental treatment is composed of a liquid material containing a radically polymerizable (meth)acrylic monomer such as a lower alkyl(meth)acrylate-based monomer as the main component and a powder material containing a non-crosslinked resin such as polymethyl methacrylate as the main component, and a curable material is prepared by mixing together the powder material and the liquid material.
In this curable material kit, a chemical polymerization type radical polymerization initiator composed of a plurality of constituent components is used to polymerize the above radically polymerizable (meth)acrylic monomer. That is, the constituent components of this chemical polymerization type polymerization initiator are separately blended in the liquid material and the powder material so that a radical is produced when the liquid material and the powder material are mixed together to initiate the radical polymerization of the above (meth)acrylate-based monomer.
Although this chemical polymerization type radical polymerization initiator is generally a combination of an organic peroxide and an aromatic tertiary amine, a combination of a pyrimidinetrione derivative, an organic metal compound and an organic halogen compound is also known as an advantageous polymerization initiator because the discoloration of a cured product hardly occurs (refer to Patent Documents 1 and 2).
Since a cured product obtained by radical polymerization contains the non-crosslinked resin, it has the advantage of high toughness as compared with a cured product containing an inorganic filler. Therefore, the powder-liquid dental curable material kit is very useful for dental clinical applications where high toughness is required and commercialized as an adhesive resin cement material which is used for the splinting of a mobile tooth, the bonding and baoding of an orthodontic and the bonding of an artificial tooth and as a normal-temperature polymerization resin material which is used for the repair of a broken denture.
In most of these applications, a mixture of the liquid material and the powder material is often cured in the oral cavity of a patient. In this case, the amount of heat generated during curing must be small in order not to hurt the patient. Further, it is also important to control the time (curing time) elapsed until the mixture is cured according to the clinical situation.
In the above powder-liquid dental curable material kit, a technology for controlling the curing time by slowing down the curing rate moderately by using a polymerization inhibitor has been proposed in order to control the heating temperature and the curing time (refer to Patent Document 3). However, when the curing time is controlled by this method, a polymerization reaction proceeds at once after the polymerization inhibitor is used up to delay curing and disappears. Therefore, the technology is ineffective for the suppression of heat generation during curing.
Also, a technology for controlling the curing time arbitrarily and suppressing heat generation during curing without deteriorating the physical properties of a cured product by using a radical chain transfer agent has been reported (refer to Patent Document 4).